Well the two worst things I see are the welds at the front trunnion, receiver to the trunnion and the trunnion to the barrel.

The receiver welds look like they're welded right to the rivet stubs left in the trunnion and the little pieces of the rivets are breaking loose.
The barrel weld to the trunnion is the nasty looking one, it does look like you might be able to cut enough away to get it back out, but your going to need to be very careful if you try this.

This is how I'd attack it
First drill those welds on the receiver out just enough to break the surface of the receiver so you can get the trunnion out.
Then coming from the bottom of the trunnion I'd start cutting on the weld that's on the barrel. Get it as close to the barrel as possible, then clean up the rest of the welds once they are seperated.

"Government is not the solution to our problem, government is the problem" Ronald Reagan

Honestly if you don't have the tools an parts to fix it I put it on Gun broker as is . let some one else fix it. someone will pay to much for it.

I would put it on a new recvier . Id cut the weld at the trunion on a lathe an press out the barrel an toss it .

if the gun can be fixed its likely worth $500 or more in todays world. Its going to be gobbled in some way no matter what you do. back when parts were cheap id have kept the bolt an carrier an what ever else is un molested an junked the rest.

your not likey going to hurt the value by demilling it so that's the first step. before you do get it head spaced an figure out why its not firing . if the round is chambering an you rgetting a primer strike it should go bang.

also the barrel looks pinned why is it welded to the trunion ?? Drive the pin out if its actualy pinned an see whats going on. it might be plug welded If its plug welded then junk the trunion IMO

I have a lot of tools, grinders, die grinders, drill press, 20ton press, ac welders, gas welders and lots of big hammers. I want to try and put a new trunion and receiver and use the rest. Will the welds on the barrel weaken it enough to make it dangerous?

Does the barrel pin go into the other side of the trunnion?
Looking in the hole you should be able to tell, most of the pins I've seen are a little short and set in the holes a little, maybe the person just stopped short.

It sounds like you have the tools to do the job. If you want to go through with this, make sure to ask any questions, we'll try to help.

I think you should be ok with those welds, it looks like the person that did them knew what they were doing, don't look like they got the parts too hot.

"Government is not the solution to our problem, government is the problem" Ronald Reagan

There is about 3/8 of an inch sticking out on the other side. The hole on the left is buggered up a little but the pin is not in the hole much if at all. The other side of the pin does not show any damage.

Wow! that baby is a mixer. Looks to be a AK47 type FSB or a smaller diameter SLR95 type FSB with the 14/1 brake welded to it.
Barrel looks to be a WASR/SAR3 style. Not sure what trunnion?
You say it headspaces OK.
The misfires could be due to an improper hammer to firing pin interface. This is common in swapped out or 7.62 style FCG's in a WASR/SAR3. Often the hammer face must be reprofiled to strike the firing pin at the proper angle. You should be able to see this visually.
If it does headspace OK and you can get the barrel pin properly seated and function and fire consistently....,
I would be inclined to just finish up the trunnion to receiver as welds and smooth them down to flat with the receiver and do the same at the rear for a flush look build. It is already a mixer so just getting it to look decent and function 100% would be a triumph. Without dumping money in it or trying to demil all thse welds and mixed parts. A challange.

Wow! that baby is a mixer. Looks to be a AK47 type FSB or a smaller diameter SLR95 type FSB with the 14/1 brake welded to it.
Barrel looks to be a WASR/SAR3 style. Not sure what trunnion?
You say it headspaces OK.
The misfires could be due to an improper hammer to firing pin interface. This is common in swapped out or 7.62 style FCG's in a WASR/SAR3. Often the hammer face must be reproflied to strike the firing pin at the proper angle. You should be able to see this visually.
If it does headspace OK and you can get the barrel pin properly seated and function and fire consistently....,
I would be inclined to just finish up the trunnion to receiver as welds and smooth them down to flat with the receiver and do the same at the rear for a fush look build. It is already a mixer so just getting it to look decent and function 100% would be a triumph. Without dumping money in it or trying to demil all thse welds and mixed parts. A challange.

Thanks, that would be better yet if it is safe. I have read about a lot of these that have no problems, maybe a little touch up will be all it needs. No doubt I will have more problems. Still haven't figured out the magazine feed and clearance issue. The mag that came with it says "made in Bulgaria" right on the side, and it works when it fires. The other two european mags feed too high and bolt catches the bullets when you try to chamber a round. The hammer and fire pin look like a good connect but the top of the bolt shows impact so maybe it's hitting the top of the bolt before the firing pin hits the primer. I will work on the a little and see.

As much Welding as there is on the Chamber of that Barrel I would not try to use it I wouldn't fire it anywhere near my face. there is no way the temper has not been affected on that barrel. it is likely harder and more brittle than it should be.

In my opinion the gun is unsafe to shoot and many of the parts are unsafe to use.